Integrated metal gate CMOS devices

ABSTRACT

A semiconductor device comprises a first semiconductor fin arranged on a substrate, the first semiconductor fin having a first channel region, and a second semiconductor fin arranged on the substrate, the second semiconductor fin having a second channel region. A first gate stack is arranged on the first channel region. The first gate stack comprises a first metal layer arranged on the first channel region, a work function metal layer arranged on the first metal layer, and a work function metal arranged on the work function metal layer. A second gate stack is arranged on the second channel region, the second gate stack comprising a work function metal arranged on the second channel region.

DOMESTIC PRIORITY

This application is a divisional of U.S. Non-Provisional applicationSer. No. 15/198,730, entitled “INTEGRATED METAL GATE CMOS DEVICES”,filed Jun. 30, 2016, which is incorporated herein by reference in itsentirety.

BACKGROUND

The present invention generally relates to complimentary metal-oxidesemiconductors (CMOS) and metal-oxide-semiconductor field-effecttransistors (MOSFET), and more specifically, to gate stack fabrication.

The MOSFET is a transistor used for switching electronic signals. TheMOSFET has a source, a drain, and gate electrode. The gate iselectrically insulated from the main semiconductor n-channel orp-channel by a thin layer of insulating material, for example, silicondioxide or high dielectric constant (high-k) dielectrics, which makesthe input resistance of the MOSFET relatively high. The gate voltagecontrols whether the path from drain to source is an open circuit(“off”) or a resistive path (“on”).

N-type field effect transistors (nFET) and p-type field effecttransistors (pFET) are two types of complementary MOSFETs. The nFET useselectrons as the current carriers and includes n-doped source and drainjunctions. The pFET uses holes as the current carriers and includesp-doped source and drain junctions.

The FinFET is a type of MOSFET. The FinFET is a multiple-gate MOSFETdevice that mitigates the effects of short channels and reducesdrain-induced barrier lowering. The “fin” refers to a semiconductormaterial patterned on a substrate that often has three exposed surfacesthat form the narrow channel between source and drain regions. A thindielectric layer arranged over the fin separates the fin channel fromthe gate. Because the fin provides a three dimensional surface for thechannel region, a larger channel length can be achieved in a givenregion of the substrate as opposed to a planar FET device.

As CMOS scales to smaller dimensions, nanowire devices provideadvantages. A nanowire is often suspended above the substrate bysource/drain regions or the gate stack. Because the nanowire issuspended, the channel region of a nanowire device has 360 degrees ofexposed area. The gate stack can be formed around the channel region ofthe nanowire to form a gate-all-around-device. The nanowire can provideeven more surface area and greater channel length than a finFET deviceor planar FET device in a given region of a substrate. Nanowire FETs canbe formed from stacked nanowires providing even greater layout density.Stacked nanowires provide, for example, increased drive current within agiven layout area.

With the transistors scaling, the threshold voltage for differentdevices via the channel doping becomes more and more difficult forfinFET devices, nanosheet devices and nanowire devices due to complexdevice structure as well as due to the maximum available Vt tuned bychannel doping. Therefore, threshold voltage tuned by pure work functionis needed to offer the different Vt type devices. In addition, due tothe impurity scattering in the channel because of the need to have thechannel doping to change the threshold voltage, the mobility of thetransistors will be degraded and thus the performance will be impactedby channel doping to change the Vts. However, threshold voltage tuned bywork function has no such issue because no channel doping is needed. Andthus, threshold voltage tune by work function metal in the gate canoffer different Vts but without performance degradation. Therefore,threshold voltage tune by work function metal in the gate become quitecritical to have high performance chip.

Gate spacers form an insulating film along gate sidewalls. Gate spacerscan also initially be formed along sacrificial gate sidewalls inreplacement gate technology. The gate spacers are used to definesource/drain regions in active areas of a semiconductor substratelocated adjacent to the gate.

Device scaling in the semiconductor industry reduces costs, decreasespower consumption, and provides faster devices with increased functionsper unit area. Improvements in optical lithography have played a majorrole in device scaling. However, optical lithography has limitations forminimum dimensions and pitch, which are determined by the wavelength ofthe irradiation.

SUMMARY

According to an embodiment of the present invention, a method forforming semiconductor devices, comprises forming a first channel region,a second channel region, a third channel region, and a fourth channelregion on a substrate, forming a first metal layer on the first channelregion, the second channel region, the third channel region, and thefourth channel region, and forming a sacrificial block layer on thefirst metal layer and forming a sacrificial patterning layer on thesacrificial block layer. The first metal layer, the sacrificial blocklayer and the sacrificial patterning layer are removed from the firstchannel region. A barrier metal layer is formed on the first channelregion and over the sacrificial patterning layer. The first metal layer,the sacrificial block layer, the sacrificial patterning layer, and thebarrier metal layer are removed from the second channel region and thirdchannel region. The first metal layer is removed from the second channelregion and the third channel region, and the barrier metal layer, thesacrificial patterning layer are removed from the fourth channel region.The sacrificial block layer is removed from the fourth channel region. Athird metal layer and a work function metal layer are deposited on thefirst channel region, the second channel region, the third channelregion, and the fourth channel region. The third metal layer and thework function metal layer from the third channel region. A work functionmetal is deposited on the first channel region, the second channelregion, the third channel region, and the fourth channel region.

According to another embodiment of the present invention, asemiconductor device comprises a first semiconductor fin arranged on asubstrate, the first semiconductor fin having a first channel region,and a second semiconductor fin arranged on the substrate, the secondsemiconductor fin having a second channel region. A first gate stack isarranged on the first channel region. The first gate stack comprises afirst metal layer arranged on the first channel region, a work functionmetal layer arranged on the first metal layer, and a work function metalarranged on the work function metal layer. A second gate stack isarranged on the second channel region, the second gate stack comprisinga work function metal arranged on the second channel region.

According to yet another embodiment of the present invention, asemiconductor device comprises a first semiconductor fin arranged on asubstrate, the first semiconductor fin having a first channel region,and a second semiconductor fin arranged on the substrate, the secondsemiconductor fin having a second channel region. A first gate stack isarranged on the first channel region, the first gate stack includes abarrier metal layer arranged on the first channel region, a first metallayer arranged on the barrier metal layer, a work function metal layerarranged on the first metal layer, and a work function metal arranged onthe work function metal layer. A second gate stack is arranged on thesecond channel region, the second gate stack includes a first metallayer arranged on the second channel region, a sacrificial patterninglayer arranged on the first metal layer, a work function metal layerarranged on the sacrificial patterning layer, and another work functionmetal arranged on the work function metal layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-20B illustrate an exemplary method for forming four differenttypes of gate stacks on a single wafer or substrate.

FIG. 1 illustrates a side view of a semiconductor-on-insulator (SOI)wafer.

FIG. 2A illustrates a side view following the formation of fins on theinsulator layer.

FIG. 2B illustrates a top view of the fins on the insulator layer.

FIG. 3 illustrates a top view following the formation of sacrificialgates over channel regions of the fins.

FIG. 4 illustrates a top view following the formation of spacersadjacent to the sacrificial gates.

FIG. 5 illustrates a top view following the formation of source/drainregions.

FIG. 6 illustrates a top view following the formation of an inter-leveldielectric layer over the source/drain regions 502 (of FIG. 5).

FIG. 7A illustrates a cut-away view along the line A-A (of FIG. 7C).

FIG. 7B illustrates a cut-away view along the line B-B (of FIG. 7C) ofthe resultant structure following the removal of the sacrificial gates(of FIG. 6) to form cavities that expose the channel regions of thefins.

FIG. 7C illustrates a top view of the cavities and the channel regions.

FIG. 8A and FIG. 8B illustrate a cut-away views following the depositionof a first metal layer in the cavities.

FIG. 9A and FIG. 9B illustrate cut-away views following the depositionof a sacrificial block layer over the first metal layer and thesacrificial patterning layer over the sacrificial block layer.

FIG. 10A and FIG. 10B illustrate cut-away views following the patterningof a mask over the channel regions and the removal of the first metallayer, the block sacrificial layer and the sacrificial patterning layerfrom the channel region.

FIG. 11A and FIG. 11B illustrate cut-away views following the depositionof a barrier metal layer in the cavities.

FIG. 12A and FIG. 12B illustrate cut-away views following the patterningof a mask over the channel regions.

FIG. 13A and FIG. 13B illustrate cut-away views following the removal ofthe mask (of FIGS. 12A and 12B) and the patterning of the mask over thechannel region.

FIG. 14A and FIG. 14B illustrate cut-away views following the removal ofthe mask.

FIG. 15A and FIG. 15B illustrate cut-away views following the removal ofexposed portions of the sacrificial block layer (of FIG. 14B) from thechannel region using a selective etching process.

FIG. 16A and FIG. 16B illustrate cut-away views following the depositionof a third metal layer in the channel regions.

FIG. 17A and FIG. 17B illustrate cut-away views following the patterningof a mask over the channel regions and an etching process that removesthe fourth metal layer, the NFET work function metal layer, and thethird metal layer.

FIG. 18A and FIG. 18B illustrate cut-away views following the removal ofthe mask (of FIGS. 17A and 17B) and the deposition of a work functionmetal on the channel regions.

FIG. 19A and FIG. 19B illustrate cut-away views following the depositionof gate conductor materials that are deposited in the trenches.

FIG. 20A and FIG. 20B illustrate cut-away views following aplanarization process.

FIGS. 21-27 illustrate an exemplary method for selectively forming ametal capping layer over the channel regions.

FIG. 21 illustrates a cut-away view following the removal of thesacrificial gates (as shown in FIGS. 7A and 7B) to form the cavities.

FIG. 22 illustrates a cut-away view following the patterning of a maskover the channel region and the removal of the exposed metal cappingbarrier layer.

FIG. 23 illustrates a cut-away view following the removal of the maskand the top patterning layer.

FIG. 24 illustrates a cut-away view following the deposition of a metalbarrier layer/a metal capping layer over the channel regions.

FIG. 25 illustrates a cut-away view following the deposition of aninsulator layer.

FIG. 26 illustrates a cut-away view following an annealing process thatforms of a metal capping layer region in the channel region. The metalcapping layer should be between interfacial layer and the highdielectric constant material (high K) after annealing.

FIG. 27 illustrates a cut-away view following the removal of theinsulator layer, of a metal barrier layer/a metal capping layer, and themetal barrier layer in the cavities.

FIG. 28A and FIG. 28B illustrate cut-away views of resultant gatestacks.

FIG. 29 illustrates a top view of exemplary embodiments of FET devices.

FIG. 30 illustrates a top view of exemplary embodiments of FET devices.

FIG. 31 illustrates a top view of exemplary embodiments of FET devices.

DETAILED DESCRIPTION

Threshold voltage is the minimum voltage differential between the sourceregion and gate that instigates a conductive path between the source anddrain regions of a FET device. The threshold voltage of a FET device canbe partially set by the type and the arrangement of the materials in thegate stack of the device.

The methods and embodiments described herein provide for formingsemiconductor devices having different gate stacks on a single substratesuch that the resultant devices have different threshold voltages.

FIGS. 1-20B illustrate an exemplary method for forming four differenttypes of gate stacks on a single wafer or substrate.

FIG. 1 illustrates a side view of a semiconductor-on-insulator (SOI)wafer 101. The SOI wafer 101 includes an insulator layer 102 and asemiconductor substrate 104 arranged on the insulator layer 102. The SOIwafer 101 can be formed by any suitable technique such as, for examplewafer bonding, Smartcut™, SIMOX (Separation by IMplanted Oxygen).

The semiconductor substrate 104 can include, for example, silicon,germanium, silicon germanium, silicon carbide, and those consistingessentially of III-V compound semiconductors having a compositiondefined by the formula

AlX1GaX2InX3AsY1PY2NY3SbY4, where X1, X2, X3, Y1, Y2, Y3, and Y4represent relative proportions, each greater than or equal to zero andX1+X2+X3+Y1+Y2+Y3+Y4=1 (1 being the total relative mole quantity). Othersuitable substrates include II-VI compound semiconductors having acomposition ZnAlCdA2SeB1TeB2, where A1, A2, B1, and B2 are relativeproportions each greater than or equal to zero and A1+A2+B1+B2=1 (1being a total mole quantity). The semiconductor substrate can alsocomprise an organic semiconductor or a layered semiconductor such as,for example, Si/SiGe, a silicon-on-insulator or a SiGe-on-insulator. Aportion or entire semiconductor substrate can be amorphous,polycrystalline, or monocrystalline. In addition to the aforementionedtypes of semiconductor substrates, the semiconductor substrate employedin the present invention can also comprise a hybrid oriented (HOT)semiconductor substrate in which the HOT substrate has surface regionsof different crystallographic orientation. The semiconductor substratecan be doped, undoped or contain doped regions and undoped regionstherein. The semiconductor substrate can contain regions with strain andregions without strain therein, or contain regions of tensile strain andcompressive strain.

The insulator layer 102 can include, for example, a buried oxide (BOX)material or other suitable insulator materials. Examples of suitableinsulator materials include silicon oxide, silicon nitride, siliconoxynitride, boron nitride, high-k materials, or any combination of thesematerials. Examples of high-k materials include but are not limited tometal oxides such as hafnium oxide, hafnium silicon oxide, hafniumsilicon oxynitride, lanthanum oxide, lanthanum aluminum oxide, zirconiumoxide, zirconium silicon oxide, zirconium silicon oxynitride, tantalumoxide, titanium oxide, barium strontium titanium oxide, barium titaniumoxide, strontium titanium oxide, yttrium oxide, aluminum oxide, leadscandium tantalum oxide, and lead zinc niobate. The high-k can furtherinclude dopants such as lanthanum, aluminum.

The thickness of insulator layer 102 generally varies and is notintended to be limited. In one aspect, the thickness of the insulatorlayer 102 is in a range from about 10 nm to about 1000 nm. The insulatorlayer 102 can be formed by any suitable process such as thermaloxidation, thermal nitridation, chemical vapor deposition (CVD).

A hardmask layer 106 is arranged on the semiconductor substrate 104. Thehardmask 106 can include, for example, silicon oxide, silicon nitride(SiN), SiOCN, SiBCN or any suitable combination of those. The hardmask106 can be deposited using a deposition process, including, but notlimited to, PVD, CVD, PECVD, or any combination thereof.

Though the illustrated exemplary embodiment includes asemiconductor-on-insulator wafer 101, alternate exemplary embodimentscan be formed on a bulk semiconductor substrate. With a bulk substrate,an additional shallow trench insulator can be formed on the substrateand between the fins 202.

FIG. 2A illustrates a side view following the formation of fins 202 onthe insulator layer 102. The fins 202 can be patterned by, for example,a lithographic patterning and etching process such as, reactive ionetching (RIE) or a sidewall imaging transfer process that removesexposed portions of the hardmask 106 and portions of the semiconductorsubstrate 104 to expose portions of the insulator layer 102. FIG. 2Billustrates a top view of the fins 202 on the insulator layer 102.

FIG. 3 illustrates a top view following the formation of sacrificialgates 302 over channel regions of the fins 202.

The sacrificial gates 302 in the exemplary embodiment are formed bydepositing a layer (not shown) of sacrificial gate material such as, forexample, amorphous silicon (aSi), or polycrystalline silicon(polysilicon) material or another suitable sacrificial gate materiallike W. The sacrificial gate 302 can further comprises a sacrificialgate dielectric material such as silicon oxide between the nanowires andaSi or polysilicon material.

The layer sacrificial gate material can be deposited by a depositionprocess, including, but not limited to, physical vapor deposition (PVD),chemical vapor deposition (CVD), atomic layer deposition (ALD, plasmaenhanced chemical vapor deposition (PECVD), inductively coupled plasmachemical vapor deposition (ICP CVD), or any combination thereof.

Following the deposition of the layer of sacrificial gate material, ahard mask layer (not shown) such as, for example, silicon oxide, siliconnitride (SiN), SiOCN, SiBCN or any suitable combination of thosematerials, is deposited on the layer of sacrificial gate material toform a PC hard mask or sacrificial gate cap (not shown). The hardmasklayer can be deposited using a deposition process, including, but notlimited to, PVD, CVD, PECVD, or any combination thereof.

Following the deposition of the layer sacrificial gate material and thehardmask layer, a lithographic patterning and etching process such as,for example, reactive ion etching or a wet etching process is performedto remove exposed portions of the hardmask layer and the layer ofsacrificial gate material form the sacrificial gates 302 and thesacrificial gate caps.

FIG. 4 illustrates a top view following the formation of spacers 402adjacent to the sacrificial gates 302. The spacers 402 in theillustrated embodiment are formed by depositing a layer of spacermaterial (not shown) over the exposed portions of the insulator layer102, the fins 202, and the sacrificial gates 302. Non-limiting examplesof suitable materials for the layer of spacer material includedielectric oxides (e.g., silicon oxide), dielectric nitrides (e.g.,silicon nitride), dielectric oxynitrides, or any combination thereof.The layer of spacer material is deposited by a suitable depositionprocess, for example, chemical vapor deposition (CVD) or physical vapordeposition (PVD).

Following the deposition of the layer of spacer material, a suitableanisotropic etching process such as, for example, a reactive ion etchingprocess is performed to remove portions of the layer of spacer materialon any flat regions to form the spacers 402.

FIG. 5 illustrates a top view following the formation of source/drainregions 502. The source/drain regions 502 are formed by an epitaxialgrowth process that deposits a crystalline overlayer of semiconductormaterial onto the exposed crystalline seed material of the exposed fin202 to form the source/drain regions 502.

Epitaxial materials can be grown from gaseous or liquid precursors.Epitaxial materials can be grown using vapor-phase epitaxy (VPE),molecular-beam epitaxy (MBE), liquid-phase epitaxy (LPE), or othersuitable process. Epitaxial silicon, silicon germanium, and/or carbondoped silicon (Si:C) silicon can be doped during deposition (in-situdoped) by adding dopants, n-type dopants (e.g., phosphorus or arsenic)or p-type dopants (e.g., boron or gallium), depending on the type oftransistor. The dopant concentration in the source/drain can range from1×1019 cm-3 to 2×1021 cm-3, or preferably between 2×1020 cm-3 to 1×1021cm-3.

The terms “epitaxial growth and/or deposition” and “epitaxially formedand/or grown” mean the growth of a semiconductor material (crystallinematerial) on a deposition surface of another semiconductor material(crystalline material), in which the semiconductor material being grown(crystalline overlayer) has substantially the same crystallinecharacteristics as the semiconductor material of the deposition surface(seed material). In an epitaxial deposition process, the chemicalreactants provided by the source gases are controlled and the systemparameters are set so that the depositing atoms arrive at the depositionsurface of the semiconductor substrate with sufficient energy to moveabout on the surface such that the depositing atoms orient themselves tothe crystal arrangement of the atoms of the deposition surface.Therefore, an epitaxially grown semiconductor material has substantiallythe same crystalline characteristics as the deposition surface on whichthe epitaxially grown material is formed. For example, an epitaxiallygrown semiconductor material deposited on a {100} orientated crystallinesurface will take on a {100} orientation. In some embodiments, epitaxialgrowth and/or deposition processes are selective to forming onsemiconductor surface, and generally do not deposit material on exposedsurfaces, such as silicon dioxide or silicon nitride surfaces.

In some embodiments, the gas source for the deposition of epitaxialsemiconductor material include a silicon containing gas source, agermanium containing gas source, or a combination thereof. For example,an epitaxial Si layer can be deposited from a silicon gas source that isselected from the group consisting of silane, disilane, trisilane,tetrasilane, hexachlorodisilane, tetrachlorosilane, dichlorosilane,trichlorosilane, methylsilane, dimethylsilane, ethylsilane,methyldisilane, dimethyldisilane, hexamethyldisilane and combinationsthereof. An epitaxial germanium layer can be deposited from a germaniumgas source that is selected from the group consisting of germane,digermane, halogermane, dichlorogermane, trichlorogermane,tetrachlorogermane and combinations thereof. While an epitaxial silicongermanium alloy layer can be formed utilizing a combination of such gassources. Carrier gases like hydrogen, nitrogen, helium and argon can beused.

FIG. 6 illustrates a top view following the formation of an inter-leveldielectric layer 602 over the source/drain regions 502 (of FIG. 5). Theinter-level dielectric layer 602 is formed from, for example, a low-kdielectric material (with k<4.0), including but not limited to, siliconoxide, spin-on-glass, a flowable oxide, a high density plasma oxide,borophosphosilicate glass (BPSG), or any combination thereof. Theinter-level dielectric layer 602 is deposited by a deposition process,including, but not limited to CVD, PVD, plasma enhanced CVD, atomiclayer deposition (ALD), evaporation, chemical solution deposition, orlike processes. Following the deposition of the inter-level dielectriclayer 602, a planarization process such as, for example, chemicalmechanical polishing is performed.

FIG. 7A illustrates a cut-away view along the line A-A (of FIG. 7C) andFIG. 7B illustrates a cut-away view along the line B-B (of FIG. 7C) ofthe resultant structure following the removal of the sacrificial gates302 (of FIG. 6) to form cavities 702 a and 702 b that expose the channelregions of the fins 202. The sacrificial gates 302 can be removed byperforming a dry etch process, for example, ME, followed by a wet etchprocess. The wet etch process is selective to (will not substantiallyetch) the spacers 402 and the inter-level dielectric material. Thechemical etch process can include, but is not limited to, hot ammonia ortetramethylammonium hydroxide (TMAH). FIG. 7C illustrates a top view ofthe cavities 702 a and 702 b and the channel regions 202 a, and 202 carranged in the first cavity 702 a and the channel regions 202 b and 202d arranged in the second cavity 702 b.

Following the removal of the sacrificial gates 302, an interfacial layersuch as, for example, SiO2 or SiN can be formed conformally over theexposed channel regions of the fins 202. Following the formation of theinterfacial layer, a high k dielectric layer is deposited over theinterfacial layer. Following the formation of the high k dielectriclayer, the first metal layer 802 (described below) can be formed. In anembodiment, the first metal layer 802 is TiN. The first metal layer isfrom 20 angstrom to 60 angstrom. For clarity, the interfacial layer andthe high k dielectric layer will be shown in FIGS. 20A and 20B that aredescribed below.

FIG. 8A and FIG. 8B illustrate a cut-away views following the depositionof a first metal layer 802 in the cavities 702 a and 702 b. In theillustrated exemplary embodiment, the first metal layer 802 has athickness of about 20 Å or less. The first metal layer 802 and otherdielectric materials can be formed by suitable deposition processes, forexample, chemical vapor deposition (CVD), plasma-enhanced chemical vapordeposition (PECVD), atomic layer deposition (ALD), evaporation, physicalvapor deposition (PVD), chemical solution deposition, or other likeprocesses.

FIG. 9A and FIG. 9B illustrate cut-away views following the depositionof a sacrificial block layer 902 over the first metal layer 802 and alayer of sacrificial patterning layer 904 over the sacrificial blocklayer 902. The sacrificial patterning layer 904 and the sacrificialblock layer 902 could be metal layer or dielectric layer. The individualthickness of these two layers is about 10 Å or less.

FIG. 10A and FIG. 10B illustrate cut-away views following the patterningof a mask 1002 over the channel regions 202 b, 202 c, and 202 d and theremoval of the first metal layer 802, the sacrificial block layer 902and the sacrificial patterning layer 904 from the channel region 202 a.The mask 1002 can include, for example, a resist mask or an organicplanarization layer that has been patterned using a resist mask andetching process. The first metal layer 902, the sacrificial block layer902 and the sacrificial patterning layer 904 can be removed from thechannel region 202 a, by for example, an etching process such asreactive ion etching.

FIG. 11A and FIG. 11B illustrate cut-away views following the depositionof a barrier metal layer 1102 in the cavities 702 a and 702 b. The mask1002 (of FIGS. 10A and 10B) can be removed by a suitable process suchas, for example, ashing. The ashing process can be used to remove aphotoresist material, amorphous carbon, or organic planarization (OPL)layer. Ashing is performed using a suitable reaction gas, for example,O2, N2, H2/N2, O3, CF4, or any combination thereof.

FIG. 12A and FIG. 12B illustrate cut-away views following the patterningof a mask 1202 over the channel regions 202 a and 202 d. Following thepatterning of the mask 1202, an etching process is performed thatremoves exposed portions of the barrier metal layer 1102, thesacrificial block layer 902 and the sacrificial patterning layer 904 toexpose the first metal layer 802 in over the channel regions 202 b and202 c. In one embodiment, the barrier metal layer 1102 is TiN. Thebarrier metal layer 1102 is from 1 angstrom to 25 angstrom.

FIG. 13A and FIG. 13B illustrate cut-away views following the removal ofthe mask 1202 (of FIGS. 12A and 12B) and the patterning of the mask 1302over the channel region 202 a. Once the mask 1302 is formed, a selectiveetching process is performed to remove the exposed portions of the firstmetal layer 802 from the channel regions 202 b and 202 c. The etchingprocess removes the exposed portions of the barrier metal layer 1102 andthe sacrificial patterning layer 904 to expose the sacrificial blocklayer 902 in the channel region 202 d.

FIG. 14A and FIG. 14B illustrate cut-away views following the removal ofthe mask 1302. FIG. 15A and FIG. 15B illustrate cut-away views followingthe removal of exposed portions of the sacrificial block layer 902 (ofFIG. 14B) from the channel region 202 d using a selective etchingprocess.

FIG. 16A and FIG. 16B illustrate cut-away views following the depositionof a third metal layer 1602 in the channel regions 202 a, 202 b, 202 c,and 202 d. Following the deposition of the third metal layer 1602, aNFET work function metal layer 1604 is deposited on the third metallayer 1602 and a fourth metal layer 1606 is deposited on the NFET workfunction metal layer 1604 in the channel regions 202 a, 202 b, 202 c,and 202 d. The third metal layer 1602 or the fourth metal layer 1606 areoptional in some exemplary embodiments. The nFET work function metalcould be TiAl, Al, Ti, TiAlC, TaAlC, and any combination thereof. In oneembodiment, the third metal layer 1602 is TiN. In another embodiment,the fourth metal layer 1606 is TiN. The third metal layer 1602 is from 1angstrom to 25 angstrom. And the fourth metal layer 1606 is from 1angstrom to 25 angstrom. In one embodiment, the fourth metal layer 1606is optional. The nFET work function metal thickness is from 10 angstromto 100 angstrom.

FIG. 17A and FIG. 17B illustrate cut-away views following the patterningof a mask 1702 over the channel regions 202 a, 202 b, and 202 d and anetching process that removes the fourth metal layer 1606, the NFET workfunction metal layer 1604, and the third metal layer 1602 to expose thechannel region 202 c.

FIG. 18A and FIG. 18B illustrate cut-away views following the removal ofthe mask 1702 (of FIGS. 17A and 17B) and the deposition of a workfunction metal 1802 on the channel regions 202 a, 202 b, 202 c, and 202d.

The type of work function metal(s) 1802 depends on the type oftransistor and can differ between the nFET and pFET devices.Non-limiting examples of suitable work function metals 1802 includep-type work function metal materials and n-type work function metalmaterials. P-type work function materials include compositions such asruthenium, palladium, platinum, cobalt, nickel, and conductive metaloxides, or any combination thereof. N-type metal materials includecompositions such as hafnium, zirconium, titanium, tantalum, aluminum,metal carbides (e.g., hafnium carbide, zirconium carbide, titaniumcarbide, and aluminum carbide), aluminides, or any combination thereof.The work function metal(s) can be deposited by a suitable depositionprocess, for example, CVD, PECVD, PVD, plating, thermal or e-beamevaporation, and sputtering. In one embodiment, the work function metal1802 is TiN.

FIG. 19A and FIG. 19B illustrate cut-away views following the depositionof gate conductor 1902 materials that are deposited in the trenches 702a and 702 b. The gate conductor 1902 material(s) is deposited over thegate dielectric materials and work function metal(s). Non-limitingexamples of suitable conductive metals include aluminum (Al), platinum(Pt), gold (Au), tungsten (W), titanium (Ti), or any combinationthereof. The gate conductor 1902 material(s) can be deposited by asuitable deposition process, for example, CVD, PECVD, PVD, plating,thermal or e-beam evaporation, and sputtering.

FIG. 20A and FIG. 20B illustrate cut-away views following aplanarization process such as, for example, chemical mechanicalpolishing (CMP), which is performed to remove the overburden of thedeposited gate materials and form the gate stacks 2002 a, 2002 b 2002 cand 2002 d over the channel regions 202 a, 202 b, 202 c, and 202 drespectively.

Each of the gate stacks 2002 a, 2002 b 2002 c and 2002 d have differentmaterial arrangements such that the voltage thresholds of the gatestacks 2002 a, 2002 b 2002 c and 2002 d are different and the type ofresultant devices are different. In the illustrated exemplaryembodiment, the gate stack 2002 a is an n-type gate stack with arelatively higher threshold voltage than the gate stack 2002 b, that isan n-type gate stack with a relatively lower threshold voltage. The gatestack 2002 d is a p-type gate stack with a relatively higher thresholdvoltage than the threshold voltage of the p-type gate stack 2002 c.

The gate stacks 2002 a-d each have an interfacial layer 2001 and a highk dielectric layer 2003 that are formed prior to forming the first metallayer 802 (of FIG. 8A).

FIGS. 21-27 illustrate an exemplary method for forming a metal cappinglayer over the channel region 202 c while not forming a metal cappinglayer over the channel region 202 d. The method described in FIGS. 21-28can be performed prior to forming the gates 202 a-d described above. Themetal capping layer can be selectively formed under any or all of thegates 202 a-d, which can be used to further change the threshold voltageof the gates a-d. In other words, the metal capping layer can be formedin a channel region of a device prior to forming a gate stack to furthertune the threshold voltage of a particular device.

In this regard, FIG. 21 illustrates a cut-away view following theremoval of the sacrificial gates 302 (as shown in FIGS. 7A and 7B) toform the cavities 702 a and 702 b. FIG. 21 shows the resultant structurefollowing the deposition of an interfacial layer 2001, which can be usedwhen forming the metal capping layer or prior to forming gate stacks2002 a-d described above. The interfacial layer can include, forexample, SiO2 or SiON. Following the formation of the interfacial layer2001, a high k dielectric layer 2003 is formed on the interfacial layer2001. A metal capping barrier layer 2102 is deposited on the high kdielectric layer 2003. The metal capping barrier layer 2102 can include,for example, TiN or other metal layers.

FIG. 22 illustrates a cut-away view following the patterning of a mask2202 over the channel region 202 d and the removal of the exposed metalcapping barrier layer 2104 using a suitable selective etching processsuch as, for example, reactive ion etching.

FIG. 23 illustrates a cut-away view following the removal of the mask2202.

FIG. 24 illustrates a cut-away view following the deposition of a metalcapping layer 2402 over the channel regions 202 c and 202 d.

FIG. 25 illustrates a cut-away view following the deposition of a layerof a semiconductor material 2502 such as, for example, amorphous siliconin the trenches 702 a and 702 b.

FIG. 26 illustrates a cut-away view following an annealing process thatforms the metal capping layer region 2602 in the channel region 202 c.The annealing process heats the wafer and causes dopants to move fromthe metal capping layer 2402 into the semiconductor material of thechannel region 202 c to form the metal capping layer region 2602. Onemetal layer (not shown here) may be deposited on top of the metalcapping layer.

FIG. 27 illustrates a cut-away view following the removal of thesemiconductor material 2502, the metal capping layer 2402, and the metalcapping barrier layer 2102 in the cavities 702 a and 702 b. The channelregion 202 c includes the metal capping layer region 2602 while thechannel region 202 d does not include a metal capping layer region 2602.

The method described in FIGS. 21-27 provides for selectively forming ametal capping layer 2602 on a channel region of a device prior toforming the gate stacks 2002 a-d. Using the method in FIGS. 21-27 any ofthe gate stacks 2002 a-d can have a metal capping layer 2602 arranged inthe underlying channel regions 202 a-d if desired.

FIG. 28A and FIG. 28B illustrate cut-away views of gate stacks 2802 a2802 b, 2802 c, and 2802 d, which are similar to the gate stacks 2002 a,2002 b, 2002 c and 2002 d respectively, however each of the gate stacks2802 a-d include a metal capping layer 2602 arranged in the channelregions 202 a-d respectively.

FIG. 29 illustrates a top view of exemplary embodiments of FET devicesthat can be formed using the methods described above. In this regard,the device 2902 includes a gate stack 2002 b arranged adjacent to a gatestack 2002 c. The device 2904 includes a gate stack 2002 a arrangedadjacent to a gate stack 2002 d.

FIG. 30 illustrates a top view of exemplary embodiments of FET devicesthat can be formed using the methods described above. In this regard,the device 3002 includes a gate stack 2802 b arranged adjacent to a gatestack 2002 d. The device 3004 includes a gate stack 2802 a arrangedadjacent to a gate stack 2002 c.

FIG. 31 illustrates a top view of exemplary embodiments of FET devicesthat can be formed using the methods described above. In this regard,the device 3102 includes a gate stack 2002 b arranged adjacent to a gatestack 2802 c. The device 3104 includes a gate stack 2002 a arrangedadjacent to a gate stack 2802 c.

After the gate stacks are formed, additional insulating material (notshown) can be deposited over the device(s). The insulating material canbe patterned to form cavities (not shown) that expose portions of thesource/drain region 502 and the gate stacks. The cavities can be filledby a conductive material (not shown) and, in some embodiments, a linerlayer (not shown) to form conductive contacts (not shown).

The methods and resultant structures described herein provide forforming gate stacks having different layers and different thresholdvoltages on the same substrate or wafer. The different thresholdvoltages allow the overall performance of the designed integratedcircuit to be improved while reducing the scale of the semiconductordevices.

As used herein, the terms “invention” or “present invention” arenon-limiting terms and not intended to refer to any single aspect of theparticular invention but encompass all possible aspects as described inthe specification and the claims. The term “on” can refer to an elementthat is on, above or in contact with another element or featuredescribed in the specification and/or illustrated in the figures.

As used herein, the term “about” modifying the quantity of aningredient, component, or reactant of the invention employed refers tovariation in the numerical quantity that can occur, for example, throughtypical measuring and liquid handling procedures used for makingconcentrates or solutions. Furthermore, variation can occur frominadvertent error in measuring procedures, differences in themanufacture, source, or purity of the ingredients employed to make thecompositions or carry out the methods, and the like. In one aspect, theterm “about” means within 10% of the reported numerical value. Inanother aspect, the term “about” means within 5% of the reportednumerical value. Yet, in another aspect, the term “about” means within10, 9, 8, 7, 6, 5, 4, 3, 2, or 1% of the reported numerical value.

It will also be understood that when an element, such as a layer,region, or substrate is referred to as being “on” or “over” anotherelement, it can be directly on the other element or intervening elementscan also be present. In contrast, when an element is referred to asbeing “directly on” or “directly over” “on and in direct contact with”another element, there are no intervening elements present, and theelement is in contact with another element.

It will also be understood that when an element is referred to as being“connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements can bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements present.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

What is claimed is:
 1. A semiconductor device comprising: a first semiconductor fin arranged on a substrate, the first semiconductor fin having a first channel region; a second semiconductor fin arranged on the substrate, the second semiconductor fin having a second channel region; a first gate stack arranged on the first channel region, the first gate stack comprising: a first metal layer arranged on the first channel region; a work function metal layer arranged on the first metal layer; and another work function metal arranged on the work function metal layer; and a second gate stack arranged on the second channel region, the second gate stack comprising a work function metal arranged on the second channel region.
 2. The device of claim 1, wherein the first gate stack further comprises a sacrificial patterning layer arranged on the work function metal layer.
 3. The device of claim 1, further comprising a third channel region.
 4. The device of claim 3, further comprising a fourth channel region.
 5. The device of claim 4, further comprising an interfacial layer on the first channel region, the second channel region, the third channel region, and the fourth channel region.
 6. The device of claim 1, wherein the substrate is doped.
 7. The device of claim 1, wherein the substrate is undoped.
 8. The device of claim 1, wherein the substrate includes doped regions.
 9. The device of claim 1, wherein the substrate includes doped regions and undoped regions.
 10. The device of claim 5, wherein the interfacial layer include SiO₂.
 11. The device of claim 5, wherein the interfacial layer include SiN.
 12. A semiconductor device comprising: a first semiconductor fin arranged on a substrate, the first semiconductor fin having a first channel region; a second semiconductor fin arranged on the substrate, the second semiconductor fin having a second channel region; a first gate stack arranged on the first channel region, the first gate stack comprising: a barrier metal layer arranged on the first channel region; a first metal layer arranged on the barrier metal layer; a work function metal layer arranged on the first metal layer; and another work function metal arranged on the work function metal layer; and a second gate stack arranged on the second channel region, the second gate stack comprising: a first metal layer arranged on the second channel region; a sacrificial patterning layer arranged on the first metal layer; a work function metal layer arranged on the second nitride layer; and another work function metal arranged on the work function metal layer.
 13. The device of claim 12, wherein the first gate stack further comprises a sacrificial patterning layer arranged on the work function metal layer.
 14. The device of claim 12, wherein the second gate stack further comprises a third metal layer arranged on the work function metal layer.
 15. The device of claim 12, wherein the first metal layer includes TiN.
 16. The device of claim 12, further comprising a high k dielectric layer arranged on the first channel region and the second channel region.
 17. The device of claim 12, wherein the work function metal layer is selected from the group consisting of TiAl and Al.
 18. The device of claim 12, wherein the work function metal layer is selected from the group consisting of Ti, TiAlC, and TaAlC.
 19. The device of claim 12, further comprising an interfacial layer on the first channel region and the second channel region.
 20. The device of claim 14, further comprising a metal capping layer arranged on the first channel region. 